1. Field Of Invention
This invention relates to an endless seamless drying belt suitable for use in electrophotography and, more specifically, to an endless seamless drying belt comprising or coated with an absorbing material that has a high affinity to carrier fluids used in liquid inks for electrophotography.
2. Background
In electrophotography, an organophotoreceptor in the form of a plate, belt, or drum having an electrically insulating photoconductive element on an electrically conductive substrate is imaged by first uniformly electrostatically charging the surface of the photoconductive element, and then exposing the charged surface to a pattern of light. The light exposure selectively dissipates the charge in the illuminated areas, thereby forming a pattern of charged and uncharged areas. A liquid or solid powder ink is then deposited in either the charged or uncharged areas to create a toned image on the surface of the photoconductive element. The resulting visible ink image can be fixed to the photoreceptor surface or transferred to a surface of a suitable receiving medium such as sheets of material, including, for example, paper, metal, metal coated substrates, composites and the like. The imaging process can be repeated many times on the reusable photoconductive element.
The photoconductive element usually comprises a charge generating layer, a charge transport layer, and optionally other layers such as a barrier layer, a release layer, an adhesive layer, and a sub-layer. The purpose of the charge generating material is to assist in the generation of charge carriers (i.e., holes or electrons) upon exposure to light. The purpose of the charge transport material is to assist in accepting these charge carriers and transport them through the charge transport layer in order to discharge a surface charge on the photoconductive element.
In some electrophotographic imaging systems, the latent images are formed and developed on top of one another in a common imaging region of the organophotoreceptor. The latent images can be formed and developed in multiple passes of the photoconductor around a continuous transport path (i.e., a multi-pass system). Alternatively, the latent images can be formed and developed in a single pass of the photoconductor around the continuous transport path. A single-pass system enables the multi-color images to be assembled at extremely high speeds relative to the multi-pass pass system. At each color development station, liquid color developers are applied to the photoconductor belt, for example by electrically biased rotating developer rolls. The colored liquid developer (or ink) is made of small colored pigment particles dispersed in an insulating liquid (i.e., a carrier liquid).
Excess carrier liquid deposited on the photoconductor belt may stain and smudge the image, and/or cause problems in transferring the image to the transfer roll or output substrate. As such, a liquid removal mechanism such as a squeegee roll may be used immediately after each developer roll to remove excess carrier liquid deposited on the photoconductor belt at each color station. However, before the developed image is transferred to an output substrate, further drying of the image is typically required to remove all (or most all of) any remaining carrier liquid.
U.S. Pat. No. 5,420,675 to Thompson et al. teaches a drying system that uses a film forming drying roll. The drying roll is in contact with the imaged side of the photoconductor belt. The film forming drying roll has a thin, outer layer that is carrier liquid-phillic and an inner layer that is carrier liquid-phobic and compliant. As the drying roller contacts the organophotoreceptor during the electrophotographic process, the carrier liquid entrains in the carrier liquid-philic layer and is later removed from it by heating the liquid to a temperature greater than the flash point of the carrier liquid.
U.S. Pat. No. 5,552,869 to Schilli et al. discloses a drying method and apparatus for electrophotography using liquid inks. The drying apparatus removes excess carrier liquid from an image produced by liquid electrophotography on a moving organophotoreceptor belt. The system includes a drying roll that contacts the organophotoreceptor, with an outer layer that absorbs and desorbs the carrier liquid and an inner layer having a Shore A hardness of 10 to 60 which is carrier liquid-phobic, and a heating means to increase the temperature of the drying roll to no more than 5xc2x0 C. below the flash point of the carrier liquid. In one embodiment, the heating means includes two hot rolls and the system further includes a cooling means that cool the drying roll.
U.S. Pat. No. 5,736,286 to Kaneko et al. discloses the employment of a drying belt to remove carrier fluids in liquid inks. However, current techniques to manufacture drying belts have largely relied on belts where the two ends of the belt material have been lapped or overlapped to form the seam or have butted against one another to form a seam. The seam is then fastened by heat or other means of adhesion such as by the use of an adhesive or welding techniques, such as ultrasonic welding or laser welding. The resulted seamed belt causes undesirable seamed marks on prints.
This invention features a seamless drying belt having a seamless belt substrate and an absorbing material that removes carrier fluid from the plated images on the organophotoreceptor belt before transferred to the transfer roll. The seamless drying belt does not cause any seam mark on prints.
In a first aspect, the invention features a seamless drying belt that includes:
(a) a seamless substrate; and
(b) an absorbent layer on the seamless substrate wherein the absorbent layer comprising an absorbing material for carrier liquid of an electrophotographic toner.
In a second aspect, the invention features a process of preparing a seamless drying belt for electrophotographic imaging process that includes the steps of:
(a) mounting a seamless substrate on a belt mount;
(b) applying an absorbent layer comprising an absorbing material for carrier liquid of an electrophotographic toner on the seamless substrate; and
(c) curing the absorbent layer by heat.
In the description of the process, steps are separated by alphanumeric headings for convenience, not necessarily for identifying a sequence. The same is true for the applying of the various voltages. The numbering of the voltages is for identification purpose. The voltages can be applied in any order as long as they are done before the imagewise exposing step. As is apparent to one skilled in the art, the sequence of steps may be reversed, such as the order in which the individual dispersions are prepared, and the like. Unless a sequence of steps is identified as being in sequence, no sequence is required, except for those necessarily in sequence, as where a dispersion is coated, and the solids should have been dispersed before coating.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.